1. Field Of The Invention
This invention relates to drill chucks for use with manual or power impact or hammer drivers. Such tools are capable of reciprocatory or percussion action as well as rotary motion. More particularly, the present invention relates to a chuck which will maintain a secure grip on a tool without the need to frequently retighten the chuck.
2. Prior Art
Both hand and power tool impact drivers are well known. Although masonry twist drills are the most common tools used with such drivers, the drivers may also be used for cutting or abrading operations. Since the tools may have shanks of varying diameter or the cross-section of the tool shank may be polygonal, the device is usually provided with a chuck which is adjustable over a relatively wide range. The chuck may be attached to the driver by a threaded or tapered bore.
A wide variety of chucks has been developed by the art. In the simplest form of chuck, three jaws spaced circumferentially 120.degree. apart from each other are constrained by a conical body threaded onto the drive shaft so that rotation of the body in one direction relative to the drive shaft forces the jaws into gripping relationship with respect to the cylindrical shank of a tool, while rotation in the opposite direction releases the gripping relationship. Such a chuck may be keyless if the body is rotated by hand, or may require a key to develop sufficient torque to tighten or loosen the jaws.
A perceived disadvantage of presently known keyed and keyless chucks is the tendency of the chuck jaws to lose their grip on the tool shank due to longitudinal vibrations transmitted through the chuck and tool during operation of the tool. It is therefore an object of the present invention to provide a tool chuck for use in impact tools which is less susceptible to loosening than presently known devices.
Other known chucks (such as the "jaw pusher" or "Albrecht" type designs) tend to become tighter with use, which can make them difficult to open. It is therefore another object of this invention to provide an impact tool chuck which does not become unduly difficult to open as a result of use.